Corrosion inhibition



United States PatentOf CORROSION INHIBITION Wayne L. Denman, Oak Park, Ill., assignor to Dearborn Chemical Company, Chicago, 11]., a corporation of Illinois No Drawing. Filed Feb. '6, 1956, Ser. No. 563,410

12 Claims. (Cl. 106-14) The instant invention relates to aliphatic amine materials for water treating and processes of feeding such materials to water and effecting corrosion inhibition by their use in water systems or aqueous media.

In particular, the invention relates to a method of protecting the surfaces of metal pipe lines and apparatus in contact with transported aqueous media having corrosive qualities with respect to the metal. The systems wherein such media are transported are generally known as water systems, which, as the term is used herein are intended to include any of a Wide variety of systems in which water is used commercially or industrially, including steam boiler systems, steam return condensate systems, steam distribution systems, heat transfer water systems, evaporator systems, processing water systems, wet pipe fire systems, cooling water systems, etc.

In US. Patent No. 2,460,259, issued to Kahler, there is described a corrosion inhibiting method using high molecular weight amines, amine salts or amine oxides.

In US. Patent No. 2,712,531, issued to Maguire, there are described corrosion inhibiting compositions and methods involving the use of a blend of octadecyl amine and octadecyl amine acetate.

In general, it appears that a difficulty involved in the use of such high molecular weight amines per se is that they are only very slightly soluble in the ordinary aqueous medium which would preferably be used as a carrier to introduce such amines into the water system. Certain of the aliphatic amine salts are more soluble in water; but these materials tend to hydrolyze, particularly when heated in aqueous media, so as to yield corrosive acids at the point of injection into the steam system. As will be appreciated, the aliphatic amine material must be provided in relatively concentrated form in a suitable flowable carrier, such as water, so that it may be metered into the water system in which it is to be used, and wherein the aliphatic amine is maintained in a controlled but very small concentration in order to carry out its corrosion inhibiting function. The carrier system for the concentrate must, of course, not contain corrosive materials, hence water is the preferred carrier medium. In steam systems, the concentrate is heated to a relatively high temperature just at the moment that it enters into the steam system; and it is believed that hydrolysis of, for example, octadecyl amine acetate takes place at this point so as to free acetic acid which, in turn, causes corrosion at this point because of the relatively high concentration thereof. Subsequently in the steam system the concentration of any free acetic acid is so very slight that the octadecyl amine may well serve to overcome any corrosive effect. Corrosion at the point of injection of the concentrate is, however, a very disturbing problem which confronts the industry.

The instant invention is based upon the discovery of a new carrier system for the corrosion inhibiting aliphatic amine, wherein the aliphatic amine is carried in an aqueous emulsion which is stabilized by the presence Patented Oct. 18, 1960 2 c ylene oxide with a high molecular weight aliphatic amine. By the use of this condensate, in relatively, small amounts, it is possible toprepare a stable emulsion of the high molecular weight aliphatic amine inwater, in the concentrations necessary or desired for use as corrosion inhibiting concentrates. In addition, thislsysa tern also permits the presence of a volatile amine in the corrosion inhibiting aliphatic amine material into a flow of a. water-soluble condensate of at least 5 mols of .eth-

ing aqueous or condensing vapor medium. t Other and further objects, features and advantages of the present invention will become apparent to those skilled in the art from the following detailed disclosure thereof.

One aspect of the instant invention consists in a method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of add-ing'to the transporting media (a) an aliphatic amine and (b) a-water-soluble condensate of at least 5 mols of ethylene oxide with an aliphatic amine, each aliphatic radical in (a) and (b) being a C c hydrocarbon radical, (a) and (b) each being added in concentrations of not more than ppm. but sufiicient to form a protective film on the surfaces, and conveying the media sufiiciently to allow the film to form. I 1.

Another aspect of the instant invention consists in a water-treating composition comprising an aqueous aliphatic amine emulsion containing a water-soluble condensate of at least 5 mols of ethyleneoxide with an aliphatic amine, as an emulsifying agent, wherein each aliphatic radical is a Gig-C2 hydrocarbon radical, which composition may also contain a volatile amine.

The aliphatic amine which may be used per se in the practice of the invention as compound (a) or which may be used as the amine with which ethylene oxide is condensed to form compound (b), in the practice of the instant invention, is preferably a primary n-alkyl amine wherein the alkyl radical is a C C alkyl radical (or contains from 12 to 20 carbon atoms). Such aliphatic amines include lauryl (dodecyl), myristyl (tetradecyl), cetyl (hexadecyl), stearyl (octadecyl), oleyl, eicosyl (C etc. amines. The preferred amine for use as compound (a) as well as for use in the formation of compound (11) is octadecyl amine, but it will be appreciated that any of the aforementioned amines may'be employed in thepractice of the instant invention.

Ethylene oxide condensates with aliphatic amines are known per se andthe methods of producing the same are well understood by those skilled in the art. In general, the aliphatic amine is brought into contact with the desired number of mols of ethylene oxide and condensation is effected under anhydrous conditions, in the presence of an alkaline catalyst, using an elevated temperature and relatively high pressures. The resulting product contains the number of ethoxide units which corresponds to the molar ratio between the aliphatic ferred aliphatic amine for use in the preparation of the condensate is octadecyl amine. The number of mols of ethylene oxide per mol of amine which are employed is at least about 5. The number of mols employed is at least sufiicient to obtain a water dispersible or a watersoluble (i.e. colloidally soluble) aliphatic amine condensate. The desired water-solubility with various technical grades of octadecyl amine may require as much as 10 to 15 mols of ethylene oxide (in order to obtain the best results in the practice of the invention). Preferably, however, a rather subtsantial number of mols of ethylene oxide are combined with the amine, in a ratio of 40-60 mols of ethylene oxide per mol of the aliphatic amine, in order to obtain a readily soluble material which possesses the best emulsifying properties. A preferred condensate is a commercially available condensate of 50 mols of ethylene oxide with 1 mol of technical grade octadecyl amine containing approximately 96% (by weight) octadecyl amine. The maximum number of ethylene oxide units which may be formed in the condensate is merely the practical maximum number of units. The resulting condensate must, of course, be water-soluble and other than that the maximum total number of ethoxide units in the material is not important. A practical maximum is about 100 units in the molecule.

A third ingredient (c) which may be used to advantage in the practice of the instant invention is a volatile corrosion inhibiting amine. The best known members of this class of compounds are cyclohexyl amine and morpholine, both of which may be used to advantage in the practice of the instant invention (although other volatile amines such as benzylamine, etc. may be used). The volatile corrosion inhibiting amine is incorporated in the instant composition primarily for the purpose of protecting against corrosion of metal surfaces immediately above the water level in metal shipping containers and chemical mixing vats, or other water-containing systems. Also,

.the volatile amines can be incorporated in the instant emulsion without impairing the stability thereof, while at the same time serving to raise the pH and reduce any tendency toward corrosion at the point of injection.

The proportions of ingredients (a), (b) and (c) used in the practice of the instant invention are based primarily upon the most advantageous proportions for use in the emulsion concentrate. In the concentrate the weight ratio of ingredient (a) to ingredient (b) may range from about 1:1 to about 20:1. At ratios above the higher ratio just given, the effectiveness of the ethoxide condensate in stabilizing the dispersion is reduced; and at ratios below the lower ratio just recited, the additional ethoxide condensate does not serve any useful purpose. Preferably, the weight ratio of ingredient (a) to ingredient (b) is within the range from about 3:1 to about 10:1. Expressed in other terms, the weight ratio of aliphatic amine (a) to water in the emulsion for use as the concentrate may range from about 1 to 500 to about 1 to 3; and the amount of ethoxide condensate (b) present is an amount sufficient to emulsify the aliphatic amine (a) in the Water, or an amount sufficient to stabilize such emulsion.

The amount of volatile amine used in the practice of the instant invention is relatively small, since this material is intended to function in the vapor phase. In the practice of the invention, the ratio of ingredient (a) to ingredient (0) may range from about 1000:1 to about 50:1, and is preferably about 100:1.

The instant invention may be demonstrated by carrying out the following procedure:

(I) A charge of 0.5 ml. of cyclohexyl amine is added to a dispersion in 200 grams of water of grams of technical grade octadecyl amine and 10 grams of technical grade octadecyl amine acetate; and this raised the pH from 6.9 to 7.1, but the dispersion was adversely affected in that it became stringy and thick. When enough cyclohexyl amine is added to give a phenQlphthalein color to the dispersion, separation occurs.

(II) A charge of 2 ml. of cyclohexyl amine is added to a dispersion in 200 grams of water of 20 grams of technical grade octadecyl amine acetate; and this dispersion shows definite separation. A charge of 1.5 grams of a condensate of 50 mols of ethylene oxide with 1 mol of technical grade octadecyl amine (i.e. Ethomeen 18/60) is added to the separated dispersion with stirring and a substantially stab-1e dispersion is again formed.

Actually, the dispersion of procedure (11) resulting from the addition of the condensate is of only fair quality, but the dispersing effect of the condensate is clearly demonstrated. In the practice of the instant invention the amount of aliphatic amine (a) used may be replaced up to about 25% with an octadecyl amine salt such as the acetate or glycolate, particularly when the volatile amine (c) is also used to make adequate adjustment in the pH. Preferably, however, an aliphatic amine salt is not employed.

The invention may be further demonstrated by carrying out the following procedures:

(1) A charge of 180 parts of the technical octadecyl amine acetate and 20 parts of a condensate of 50 mols of ethylene oxide with 1 mol of octadecyl amine is mixed and melted together and heated to 200 F. The clear molten charge is then removed from the heat and 800 parts of hot water are added with thorough agitation; and the resulting mixture is heated to a temperature of about 170 F. and, after several minutes of stining, a thorough emulsification is obtained. The stirring is continued as the emulsion cools to 150 F. at Which time a noticeable thickening of the emulsion occurs. This preparation is then poured into glass containers and allowed to cool to room temperature at which it has a consistency of approximately cold cream. This is a stock emulsion which may be used in a package for shipment, although the emulsion actually added to a water system is approximately a 1% emulsion. A 1% emulsion is prepared by diluting the instant stock emulsion with an amount of distilled water sufiicient to obtain a 1% concentration of active ingredients (i.e. the aliphatic amine material and the condensate) and heating the resulting diluted emulsion to a temperature of about 170 F. with stirring. This results in a stable emulsion which is acid to phenolphthalein.

(2) A procedure is carried out that is the same as that described for procedure (1) except that the octadecyl amine acetate is replaced by a mixture of parts of technical octadecyl amine and 90 parts of octadecyl amine acetate and the resulting 1% emulsion has a pH under 8.2, but which is less acid than that obtained in procedure (1).

(3) A procedure is carried out that is the same as that described in procedure (1) except that the octadecyl amine acetate is replaced by parts of octadecyl amine and 45 parts of octadecyl amine acetate and a stable emulsion, at 1% concentration, is again obtained, which in this case is pink to phenolphthalein while hot and colorless when cold. The pH of the cold solution is 6.6, which again is more alkaline than the pH obtained in procedures (1) or (2).

(4) A procedure is carried out that is the same as that described in procedure (1), except that all of the octadecyl amine acetate is replaced by technical grade octadecyl amine and it is found that the 1% emulsion is stable, having a pH value of about 10.0. When equal volumes of this emulsion and the 1% emulsion obtained by procedure (3) are mixed the resulting mixture has a pH of 7.5.

(5) A procedure is carried out that is the same as that described in procedure (4), except that parts of octadecyl amine are employed and 30 parts of the ethylene oxide condensate are employed, and the resulting pH in the 1% emulsion is approximately 10.0.

(A) Apparatus for testing the pH and corrosive inhibition during simulated operating conditions was prepared assess-e including a four gallon steel container resting on a hot plate (used to obtain the desired temperature in the circulating system) equipped with a bottom outlet connected to a pump and a return line, plus an agitator. The 1% emulsions of the foregoing procedures (1-5) are tested separately in this arrangement and it is noted that an appreciable amount of corrosion beneath the water level is obtained using the emulsions of procedures (1) and (2). Less corrosion is noted in the case of the emulsion of procedure (3) (which is substantially neutral) and it is noted that practically no corrosion takes place below the liquid level using the emulsions of procedures (4) and (5). There is some corrosion above the liquid level in the case of all of the emulsions. The emulsion of procedure (5) is also diluted to V2% and concentrations and tested to give the same result as the 1% concentration.

(6) A procedure is carried out that is the same as that described in procedure (5), except that 1.5 parts of cyclohexyl amine are also added to the emulsion, and the result is a stable 1% emulsion which in the above described test procedure (A) causes substantially no corrosion above as well as below the liquid level. The pH of the 1% emulsion is 10.2.

(7) A procedure is carried out that is the same as that described in procedure (5), except that 2 parts of cyclohexyl amine are added to the emulsion and the resulting 1% emulsion is stable having a pH of 10.2 (While a 2% emulsion gives a pH of 10.3). The emulsion was tested according to procedure (A) and the results obtained were the same as those described in connection with procedure (6).

(8) A procedure is carried out that is the same as that described in procedure (7), except that 160 parts of octadecyl amine are used and 40 parts of the condensate are used; and the results are the same as those described in connection with procedure (7).

(9) A procedure is carried out that is the same as that described in connection with procedure (7), except that 150 parts of octadecyl amine are used and 50 parts of the condensate are used; and the results obtained are the same as those described in procedure (7).

(10) A procedure is carried out that is the same as that described in procedure (4) except that the condensate used is a condensate of mols of ethylene oxide with 1 mol of octadecyl amine, and it is found that rapid mechanical agitation is required to obtain a satisfactory 1% emulsion at 170 F., and rapid agitation is continued during cooling down to about 120 F., after which the mixture cools to room temperature to obtain a stable emulsion. The corrosion inhibiting properties are the same as those described for the product of procedure (4) and the pH is the same.

(11) A procedure is carried out that is the same as that described in procedure (10), except that the condensate used in a condensate of 5 mols of ethylene oxide with 1 mol of octadecyl amine, and the results obtained are substantially the same as those described in procedure (10), except that more agitation is required to effect the formation of the emulsion.

(12) A procedure is carried out that is the same as that described in procedure (4), except that the condensate used is a condensate of 50 mols of ethylene oxide with 1 mol of lauryl (dodecyl) amine, and the results obtained are the same as those described in procedure (4 (13) A procedure is carried out that is the same as that described in procedure (10), except that 1 part of cyclohexyl amine is added, and the results obtained are substantially those described in procedure (6), except that more thorough agitation is required in order to form a stable emulsion.

(14) A procedure is carried out that is the same as that described in the foregoing procedure (6), except that coconut (C -C amine is used in place of the dodecyl amine and the ethylene oxide condensate of this (C C amine is also used in place of the condensate of procedure (6); and the results obtained are substantiallythe same as those described in procedure (6).

It will thus be seen that it is possible to prepare stable emulsions using a condensate of only 5 mols ofiethylene oxide with the aliphatic amine, but this requires a greater amount of agitation than may be desirable in certain situations, and for this reason, condensates of a minimum of about 10 mols of ethylene oxide per mol of aliphaticamine are more effective for the purposes of the instantinvention, and the preferred condensates have a substan tially greater number of ethylene oxide units (i.e-., being condensates of 40-60 mols of ethylene oxide per mol er aliphatic amine). Y

In general, it i understood that these aliphatic amine materials form a thin (mono-molecular) film on the metal surface. Any metal surface may thus be protected, but low carbon steel is preferred as the structural materials for water systems which must be protected (and the test metal pieces in the test apparatus included such steel) andthis metal i afforded excellent protection. The waterused in systems protected by the invention (and in the previous demonstrations) contains the usual amount of dissolved oxygen and carbon dioxide, which are believed to be the main corrosion inducing factors in the aqueous media usually employed in water systems. Such water systems often contain water having acidcharacteristics (pH 5.5 to 6.5), but the pH may sometimes reach'a value of 8 (but ordinarily no higher).

Of course, each of the ingredients (a), (b) and (0) can be used in the ultimate aqueous or steam system in concentrations of as little as about 1 p.p-.m. and prefer ably about 2 ppm, although it is not practical to use greater than about ppm.

Another practical application involves the use of the coconut amines (particularly) in accordance with the teachings of the instant invention in the treating of flood waters used in secondary recovery of oil, whereby these amines may inhibit corosion and control basteria and algae.

It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.

I claim as my invention:

1. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of adding to the transporting media a composition con sisting essentially of (a) an aliphatic amine and (b) a water-soluble condensate of at least- 5* mols ofethylene oxide with an aliphatic amine, each aliphatic radical in (a) and (b) being a C -C hydrocarbon radical, (a) and (h) each being added in concentrations of not more than 100 p.p.m. but suflicient to form a protective film on the surfaces, and conveying the media sufficiently to allow the film to form, the weight ratio of (a):(b) ranging from 1:1 to 20:1.

2. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of adding to the transporting media a composition consisting essentially of (a) octadecyl amine and (b) a water-soluble condensate of at least 5 mols of ethylene oxide with an aliphatic amine, each aliphatic radical in (b) being a C C hydrocarbon radical, (a) and (b) each being added in concentrations of not more than 100 ppm. but suflicient to form a protective film on the surfaces, and conveying the media sufliciently to allow the film to form, the weight ratio of (a):(b) ranging from 1:1 to 20:1.

3. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqeuous media having corrosive qualities, which comprises the step of adding to the transporting media a composition consisting essentially of (a) octadecyl amine and (b) a water-soluble condensate of at least 10 mols of ethylene oxide with octadecyl amine, (a) and (b) each being added in concentrations of not more than 100 ppm. but sufficient to form a protective film on the surfaces, and conveying the media sufliciently to allow the film to form, the weight ratio of (a):(b) ranging from 3:1 to 10:1.

4. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of adding to the transporting media a composition consisting essentially of (a) an aliphatic amine and (b) a water-soluble condensate of at least 10 mols of ethylene oxide with octadecyl amine, each aliphatic radical in (a) being a C C hydrocarbon radical, (a) and (b) each being added in concentrations of not more than 100 p.p.m. but suflicient to form a protective film on the surfaces, and conveying the media sufliciently to allow the film to form, the weight ratio of (a) (b) ranging from 1:1 to 20:1.

5. A water treating composition, consisting essentially of an aqueous aliphatic amine emulsion containing a water-soluble condensate of at least 5 mols of ethylene oxide with an aliphatic amine, as an emulsifying agent, wherein each aliphatic radical is a C -C hydrocarbon radical, the weight ratio of the amine to the condensate ranging from 1:1 to 20:1.

6. A water treating composition, consisting essentially of an aqueous octadecyl amine emulsion containing a water-soluble condensate of at least 5 mols of ethylene oxide with an aliphatic amine, as an emulsifying agent, wherein each aliphatic radical is a C C hydrocarbon radical, the weight ratio of the amine to the condensate ranging from 1:1 to 20:1.

7. A water treating composition, consisting essentially of an aqueous aliphatic amine emulsion containing a water-soluble condensate of at least mols of ethylene oxide with octadecyl amine, as an emulsifying agent, wherein each aliphatic radical is a C C hydrocarbon radical, the weight ratio of the amine to the condensate ranging from 1:1 to 20:1.

8. A water treating composition, consisting essentially of an aqueous octadecyl amine emulsion containing a water-soluble condensate of 40 to 60 mols of ethylene oxide with octadecyl amine, as an emulsifying agent, the weight ratio of the amine to the condensate ranging from 3:1 to 10:1.

9. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of adding to the transporting media a composition consisting essentially of (a) an aliphatic amine; (b) a water-soluble condensate of at least 5 mols of ethylene oxide with an aliphatic amine, each aliphatic radical in (a) and (b) being a C C hydrocarbon radical; and (c) a volatile corrosion inhibiting amine; (a), (b) and (c) each being added in concentrations of not more than 100 p.p.m. but sufficient to form a protective film on the surfaces, and conveying the media sufliciently to allow the film to form, the weight ratio of (a):(b) ranging from 1:1 to 20:1 and the weight ratio of (a) :(c) ranging from 100021 to :1.

10. A method of protecting metal contacting surfaces in a continuously flowing system for transporting aqueous media having corrosive qualities, which comprises the step of adding to the transporting media a composition consisting essentially of (a) octadecyl amine; (b) a watersoluble condensate of at least 5 mols of ethylene oxide with octadecyl amine, each aliphatic radical in (a) and (b) being a C -C hydrocarbon radical; and (c) a volatile corrosion inhibiting amine; (a), (b) and (0) each being added in concentrations of not more than ppm. but suflicient to form a protective film on the surfaces, and conveying the media sufficiently to allow the film to form, the weight ratio of (a) :(b) ranging from 1:1 to 20:1 and the weight ratio of (a):(c) ranging from 1000:1 to 50:1.

11. A water treating composition, consisting essentially of an aqueous C C aliphatic amine emulsion containing a water-soluble condensate of at least 5 mols of ethylene oxide with a C C aliphatic amine, as an emulsifying agent, and a volatile corrosion inhibiting amine, the weight ratio of the aliphatic amine to the condensate ranging from 1:1 to 20:1 and the weight ratio of the aliphatic amine to the volatile amine ranging from 1000:1 to 50:1.

12. A water treating composition, consisting essentially of an aqueous octadecyl aliphatic amine emulsion containing a water-soluble condensate of at least 10 mols of ethylene oxide with octadecyl amine, as an emulsifying agent, and cyclohexyl amine, the weight ratio of the aliphatic amine to the condensate ranging from 1:1 to 20:1 and the weight ratio of the aliphatic amine to the cyclohexyl amine ranging from 1000:1 to 50:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,512,949 Lieber June 27, 1950 2,712,531 Maguire July 5, 1955 2,724,694 Troianello Nov. 22, 1955 2,739,980 Chester Mar. 27, 1956 2,779,741 Cross Jan. 29, 1957 

5. A WATER TREATING COMPOSITION, CONSISTING ESSENTIALLY OF AN AQUEOUS ALIPHATIC AMINE EMULSION CONTAINING A WATER-SOLUBLE CONDENSATE OF AT LEAST 5 MOLS OF ETHYLENE OXIDE WITH AN ALIPHATIC AMINE, AS AN EMULSIFYING AGENT, WHEREIN EACH ALIPHATIC RADICALS IS A C12-C20 HYDROCARBON RADICAL, THE WEIGHT RADIO OF THE AMINE TO THE CONDENSATE RANGING FROM 1:1 TO 20:1. 